Biology subjects

Kirkwood, P. M.

Publications and source records attributed to Kirkwood, P. M..

4 recordsLinked to original sources

bioRxiv2022

A Role for Steroid 5 alpha-reductase 1 in Vascular Remodelling During Endometrial Decidualisation

Decidualisation is the hormone-dependent process of endometrial remodelling that is essential for fertility and reproductive health. It is characterised by dynamic changes in the endometrial stromal compartment including differentiation of fibroblasts, immune cell trafficking and vascular remodelling. Deficits in decidualisation are implicated in disorders of pregnancy such as implantation failure, intra-uterine growth restriction, and pre-eclampsia. Androgens are key regulators of decidualisation that promote optimal differentiation of stromal fibroblasts and activation of downstream signalling pathways required for endometrial remodelling. We have shown that androgen biosynthesis, via 5-reductase-dependent production of dihydrotestosterone, is required for optimal decidualisation of human stromal fibroblasts in vitro, but whether this is required for decidualisation in vivo has not been tested. In the current study we used steroid 5-reductase type 1 (SRD5A1) deficient mice (Srd5a1-/- mice) and a validated model of induced decidualisation to investigate the role of SRD5A1 and intracrine androgen signalling in endometrial decidualisation. We measured decidualisation response (weight/proportion), transcriptomic changes, and morphological and functional parameters of vascular development. These investigations revealed a striking effect of 5-reductase deficiency on the decidualisation response. Furthermore, vessel permeability and transcriptional regulation of angiogenesis signalling pathways, particularly those that involved vascular endothelial growth factor (VEGF), were disrupted in the absence of 5-reductase. In Srd5a1-/- mice, injection of dihydrotestosterone co-incident with decidualisation restored decidualisation responses, vessel permeability, and expression of angiogenesis genes to wild type levels. Androgen availability declines with age which may contribute to age-related risk of pregnancy disorders. These findings show that intracrine androgen signalling is required for optimal decidualisation in vivo and confirm a major role for androgens in the development of the vasculature during decidualisation through regulation of the VEGF pathway. These findings highlight new opportunities for improving age-related deficits in fertility and pregnancy health by targeting androgen-dependent signalling in the endometrium.

physiology↗

bioRxiv2021

Single cell RNA sequencing and lineage tracing confirm mesenchyme to epithelial transformation (MET) contributes to repair of the endometrium at menstruation

The human endometrium experiences repetitive cycles of tissue wounding characterised by piecemeal shedding of the surface epithelium and rapid restoration of tissue homeostasis. In this study we used a mouse model of endometrial repair and three transgenic lines of mice to investigate whether epithelial cells that become incorporated into the newly formed luminal epithelium have their origins in one or more of the mesenchymal cell types present in the stromal compartment of the endometrium. Using scRNAseq we identified a novel population of PDGFRb+ mesenchymal stromal cells that developed a unique transcriptomic signature in response to endometrial breakdown/repair. These cells expressed genes usually considered specific to epithelial cells and in silico trajectory analysis suggested they were stromal fibroblasts in transition to becoming epithelial cells. To confirm our hypothesis we used a lineage tracing strategy to compare the fate of stromal fibroblasts (PDGFRa+) and stromal perivascular cells (NG2/CSPG4+). We demonstrated that stromal fibroblasts can undergo a mesenchyme to epithelial transformation and become incorporated into the re-epithelialised luminal surface of the repaired tissue. This study is the first to discover a novel population of wound-responsive, plastic endometrial stromal fibroblasts that contribute to the rapid restoration of an intact luminal epithelium during endometrial repair. These findings form a platform for comparisons both to endometrial pathologies which involve a fibrotic response (Ashermans syndrome, endometriosis) as well as other mucosal tissues which have a variable response to wounding. HighlightsO_LISingle cell RNA sequencing identified a population of PDGFR{beta}+ mesenchymal cells with a unique transcriptomic signature that arises in response to induction of a menses-like wound C_LIO_LIThe repair-specific mesenchymal cells express genes considered specific to both mesenchymal and epithelial lineages indicative of an intermediate phenotype and a mesenchymal to epithelial transition (MET) C_LIO_LIin silico trajectory analysis revealed that repair-specific cells originate from the fibroblast cell clusters, were distinct from perivascular cells, and had a predicted trans-differentiation trajectory towards definitive epithelial cells C_LIO_LIin vivo lineage tracing in adult mice provides definitive evidence that PDGFR+ endometrial fibroblasts, and not NG2+ perivascular cells, undergo MET and can become incorporated into the luminal epithelium of the post repair tissue C_LI

physiology↗

bioRxiv2021

The transcription factor EGR2 is indispensable for tissue-specific imprinting of alveolar macrophages in health and tissue repair

Alveolar macrophages are the most abundant macrophages in the healthy lung where they play key roles in homeostasis and immune surveillance against air-borne pathogens. Tissue-specific differentiation and survival of alveolar macrophages relies on niche-derived factors, such as colony stimulating factor 2 (CSF-2) and transforming growth factor beta (TGF-{beta}). However, the nature of the downstream molecular pathways that regulate the identity and function of alveolar macrophages and their response to injury remains poorly understood. Here, we identify that the transcriptional factor EGR2 is an evolutionarily conserved feature of lung alveolar macrophages and show that cell-intrinsic EGR2 is indispensable for the tissue-specific identity of alveolar macrophages. Mechanistically, we show that EGR2 is driven by TGF-{beta} and CSF-2 in a PPAR-{gamma}-dependent manner to control alveolar macrophage differentiation. Functionally, EGR2 was dispensable for lipid handling, but crucial for the effective elimination of the respiratory pathogen Streptococcus pneumoniae. Finally, we show that EGR2 is required for repopulation of the alveolar niche following sterile, bleomycin-induced lung injury and demonstrate that EGR2-dependent, monocyte-derived alveolar macrophages are vital for effective tissue repair following injury. Collectively, we demonstrate that EGR2 is an indispensable component of the transcriptional network controlling the identity and function of alveolar macrophages in health and disease. One Sentence SummaryEGR2 controls alveolar macrophage function in health and disease

immunology↗

bioRxiv2020

Single cell RNA sequencing redefines the mesenchymal cell landscape of mouse endometrium

The endometrium is a dynamic tissue that exhibits remarkable resilience to repeated episodes of differentiation, breakdown, regeneration and remodelling. Endometrial physiology relies on a complex interplay between the stromal and epithelial compartments with the former containing a mixture of fibroblasts, vascular and immune cells. There is evidence for rare populations of putative mesenchymal progenitor cells located in the perivascular niche of human endometrium, but the existence of an equivalent cell population in mouse is unclear. In the current study we used the Pdgfrb-BAC-eGFP transgenic reporter mouse in combination with bulk and single cell RNA sequencing (scRNAseq) to redefine the endometrial mesenchyme. Contrary to previous reports we show that CD146 is expressed in both PDGFR{beta}+ perivascular cells as well as CD31+ endothelial cells. Bulk RNAseq revealed cells in the perivascular niche which express high levels of Pdgfrb as well as genes previously identified in pericytes and/or vascular smooth muscle cells (Acta2, Myh11, Olfr78, Cspg4, Rgs4, Rgs5, Kcnj8, Abcc9). scRNAseq identified five subpopulations of cells including closely related pericytes/vascular smooth muscle cells and three subpopulations of fibroblasts. All three fibroblast populations were PDGFR+/CD34+ but were distinct in their expression of Spon2/Angptl7 (fibroblast 1), Smoc2/Rgs2 (fibroblast 2) and Clec3b/Col14a1/Mmp3 (fibroblast 3), with potential functions in regulation of immune responses, response to wounding and organisation of extracellular matrix respectively. In conclusion, these data are the first to provide a single cell atlas of the mesenchymal cell landscape in mouse endometrium. By identifying novel markers for subpopulations of mesenchymal cells we can use mouse models investigate their contribution to endometrial function, compare with other tissues and apply these findings to further our understanding of human endometrium. HighlightsO_LIGFP expression in the mouse endometrium, under the control of the Pdgfrb promoter, is restricted to two cell populations based on the intensity of GFP with GFPbright cells close to the vasculature C_LIO_LISingle cell RNAseq identified five subpopulations of GFP+ mesenchymal cells: pericytes, vascular smooth muscle cells (vSMC) and three closely related but distinct populations of fibroblasts C_LIO_LIBioinformatics revealed that pericytes and vSMC share functions associated with the circulatory system, actin-filament process and cell adhesion, and an apparent role for pericytes in smooth muscle cell migration and response to interferons C_LIO_LIComparisons between the fibroblast subpopulations suggest distinct roles in regulation of immune response, response to wound healing and collagen organisation. C_LI Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

physiology↗